Sharif Digital Repository

Effect of welding current (2–4 kA) was investigated on the microstructure evolution and mechanical properties of the upset resistance dissimilar welds of Martensitic Stainless Steel (MSS) to Duplex Stainless Steel (DSS) rods. While in MSS side of the welds, no martensite was formed at lower welding currents (2–3 kA), small values of martensite was formed at the higher welding currents (3.5–4 kA). In DSS side of the welds, hotspot formation and change in the phase balance between ferrite and austenite phase were the most important phenomena. Strength of welds first increased and then decreased with welding current. Increase of strength was related to superior plastic deformation and stronger... 

Effects of welding current (at the range of 2-4 kA) on the microstructure and mechanical properties of upset resistance welds of AISI-1035 carbon steel to AISI-304L austenitic stainless steel rods were investigated. The results showed that the joint strength first increased by raising the welding current up to 3 kA and then decreased beyond it. Increasing trend was related to more plastic deformation, accelerated diffusion, reduction of defects and formation of mechanical locks at the joint interface. For currents more than 3 kA, decrease in the joint strength was mainly caused by formation of hot spots. Using the optimum welding current of 3 kA, tensile strength of the joint reached to ~76%... 

In this research, friction stir joining of aluminum-polypropylene/talc composite was investigated due to the numerous applications of aluminum-polymer joints in automotive and aerospace industry. A novel tool design, including a rotary/stationary holder, was used to improve the appearance and mechanical performance of friction stir lap joints by preventing the mixed molten polymer and aluminum particles from exiting the stirred zone. Effect of tool transverse speed on the joint microstructure and strength was investigated. Using the rotary/stationary holder, tensile-shear strength of the joints increased (by ~ 45 to ~ 220% at various transverse speeds). Since during the tensile-shear test... 

Upset resistance dissimilar welding of aluminium and copper narrow rods was performed. Effect of the interface characteristics was studied on the joint mechanical and electrical properties. Upset resistance welding (URW) was successful for production of joints with high strength and electrical conductivity between aluminium and copper rods. Reaction layer at the joint interface was composed of the Al2Cu cellular phase and lamellar eutectic structure of α-Al and Al2Cu. Enhancement of the welding current and decrease in the upset force increased the reaction layer thickness and strength of the joint. URW had no significant detrimental effect on the electrical conductivity of the weld zone.... 

Fused Deposition Modeling with Polypropylene filament was employed to make a lap joint between Polypropylene and pre-punched Al-Mg alloy sheets, in the form of bonds between the polymeric substrate and the additive part and mechanical lock between the additive part and aluminum base sheet. Effects of the joint interface area (hole diameter of 5–13 mm) and preheating of the substrates (room temperature, 50 and 90℃) were investigated on the mechanical properties of the joints. Peak load in the tensile-shear and cross-tension tests increased with enhancement of the joint interface area (up to ˜280 N and ˜160 N, respectively). Higher joint strength in the tensile-shear test compared to the... 

Introduction: The aim of this study was to leverage label-efficient self-supervised learning (SSL) to train a model that can detect ECR and differentiate it from caries. Methods: Periapical (PA) radiographs of teeth with ECR defects were collected. Two board-certified endodontists reviewed PA radiographs and cone beam computed tomographic (CBCT) images independently to determine presence of ECR (ground truth). Radiographic data were divided into 3 regions of interest (ROIs): healthy teeth, teeth with ECR, and teeth with caries. Nine contrastive SSL models (SimCLR v2, MoCo v2, BYOL, DINO, NNCLR, SwAV, MSN, Barlow Twins, and SimSiam) were implemented in the assessment alongside 7 baseline deep...